Codeforces 584 - A problem solution

A. Olesya and Rodion

time limit per test 1 second

memory limit per test 256 megabytes

input standard input

output standard output

Olesya loves numbers consisting of n digits, and Rodion only likes numbers that are divisible by t. Find some number that satisfies both of them.

Your task is: given the n and t print an integer strictly larger than zero consisting of n digits that is divisible by t. If such number doesn't exist, print  - 1.

Input

The single line contains two numbers, n and t (1 ≤ n ≤ 100, 2 ≤ t ≤ 10) — the length of the number and the number it should be divisible by.

Output

Print one such positive number without leading zeroes, — the answer to the problem, or  - 1, if such number doesn't exist. If there are multiple possible answers, you are allowed to print any of them.

Examples

input

3 2

output

712

Problem link : https://codeforces.com/problemset/problem/584/A

Solution :

• [tab]
• C++

• #include<bits/stdc++.h>
  using namespace std;
  int main()
  {
      int n,t,i;
      cin>>n>>t;
      if(t==10)
      {
          if(n==1)
          {
              cout<<-1<<endl;
  
          }
          else{
  
              for(i=0;i<n-1;i++)
              {
                  cout<<1;
              }
              cout<<0<<endl;
          }
      }
      else{
          for(i=0;i<n;i++)
          {
              cout<<t;
          }
          cout<<endl;
      }
      return 0;
  }